1. Field of the Invention
The present invention relates to a wireless type IC chip for identification, for identifying various types of goods or persons or the like, and to a method for reading out data therefrom and a method for writing data thereinto.
2. Description of Related Art
It is a common practice to issue various IC cards or IC tags in order to identify various types of goods or people or the like. An IC card or an IC tag may be of the contact type or of the non-contact type, but the non-contact type, in which a wireless type IC chip for identification is included, is superior from the point of view of convenience during use. It should be understood that a wireless type IC chip, in addition to being included in an IC card or an IC tag, is also sometimes directly included in various types of product, such as bank notes or the like, so as to serve for identifying the product.
In order to operate its internal electronic circuitry, a prior art wireless type IC chip for identification is supplied with electrical power by taking advantage of a carrier wave from the outside (for example, refer to Patent Document Japanese Patent Laying Open Publication Heisei 10-145443). In other words, when a carrier wave from an external reader-writer is received via an on-chip antenna, along with rectifying this carrier wave so as to generate an internal power supply therefrom, data which is superimposed upon the carrier wave is also read in, so that it is possible to dispatch the necessary data by wireless.
Since, according to the above described prior art, in addition to the carrier wave from the outside serving for generation of the internal power supply for the IC chip, it is also employed as a carrier wave upon which data is superimposed, accordingly, in order accurately to demodulate the data which is thus superimposed, it is necessary to maintain the frequency of the carrier wave fixed, and thus the problem arises that the range of application becomes rather limited. In other words this is because, when the frequency of the carrier wave is fixed, it is necessary to make the characteristics of the on-chip antenna be adjusted and set so as to correspond accurately to each type of goods to which the IC chip is to be assembled, since the characteristics of the on-chip antenna which is provided upon the IC chip are influenced by the nature and the properties of the goods.